Various ink jet printing technologies have been or are being developed. One such technology, referred to hereinafter as acoustic ink printing (AIP), uses acoustic energy to produce an image on a recording medium. While more detailed descriptions of the AIP process can be found in U.S. Pat. Nos. 4,308,547, 4,697,195, and 5,028,937, essentially, bursts of acoustic energy focused near the free surface of a liquid ink cause ink droplets to be ejected onto a recording medium.
Because the dimensions of the droplet ejectors used in acoustic ink printing are small, their cleanliness is extremely important. Not only can dirt particles and dust (particularly paper dust) clog the ejector ports, but ejected ink droplets which do not adhere to the recording medium can build up enough to disrupt the printing process.
While cleanliness may be a problem with the other types of ink jet printers, such printers usually use a small, moving print head that is readily wiped clean, such as before or after the printing of each print line. However, in AIP it is contemplated that a fixed print head that spans the print line and contains thousands of individual droplet ejectors will be used. To print an image with such a print head, the recoding medium passes by the print head as droplets are ejected onto the recording medium. As can be appreciated, it is difficult to clean such a large, fixed print head by wiping, particularly with a low cost, nondestructive system that does not disrupt the printing cycle.
Therefore, a non-wiping technique for improving the cleanliness of the exposed surfaces of the droplet ejectors of a fixed print head would be beneficial.